Is there java.util.concurrent equivalent for WeakHashMap?

java collections guava java.util.concurrent weakhashmap
Nikita picture Nikita · Feb 13, 2010 · Viewed 17.9k times · Source

Can the following piece of code be rewritten w/o using Collections.synchronizedMap() yet maintaining correctness at concurrency? 

Collections.synchronizedMap(new WeakHashMap<Class, Object>());

i.e. is there something from java.util.concurrent one can use instead? Note that merely replacing with 

new ConcurrentHashMap<Class, Object>(new WeakHashMap<Class, Object>()));

obviously won't work

Answer

Steven Schlansker picture Steven Schlansker · Feb 13, 2010

Guava's CacheBuilder class allows you to do this easily.

CacheBuilder.newBuilder().weakKeys().build()

Note that this changes key equality semantics to be == instead of .equals() which will not matter in your case of using Class instances but is a potential pitfall.

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